Questions tagged [moment]

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A bar weighs 2N and is 5m in length. What is the weight(M) needed to balance the bar?

A bar weighs 2N and is 5m in length. What is the weight(M) needed to balance the bar? I think I understand that the equation not including the weight of the bar would have 3*3=(5*1)+(2*X) M=4. I don'...
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1answer
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Moment on a body and on a simply supported beam

Consider a body on a frictionless floor being acted upon by a force F as shown in figure. Force acts on its centre of mass. (Centre of mass and centre of gravity coincide in this case, ie, both lie on ...
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calculate the shear stress from surface traction

The problem is that I am simulating a hollow cylinder under torsion and I would like to compute the shear stress for it. The output of the simulation is the shear surface tractions. See the figure ...
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1answer
212 views

Difference between torque, moment and couple

I know the basics of them like Torque is force multiplied by the distance (from the point where there is no rotation like centre of gravity). Couple acts because of two equal and opposite forces ...
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26 views

Physics behind finding center of mass of a stick like object [duplicate]

If I hold a rod with both hands wherever at opposite sides of the center of mass of the body, and bring them slowly close to each other, then the point my hands meet at, is approximately the center of ...
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Teeter Totter Team Building Game

I recall doing a team building exercise where a team of about 4 people needed to balance a teeter totter, so that neither of the ends was touching the ground. They could achieve this by having the ...
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1answer
57 views

Can someone prove the Principle of Moments from Newton's Laws?

Is it possible to rigorously proof the Principle of Moments from just Newton's three laws? Here's my formulation of the laws/axioms? Someone tell me politely if I'm wrong. Particles always follow ...
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1answer
107 views

Ratchet handle force calculation

I have strap ratchet which is being pulled on both sides with some force(say 500lb). Could some one please help me know the force to be applied on the handle of the buckle to open it? Can anyone ...
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1answer
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Torque acting on car trailers

My question: "Which car trailer below will be moved in a straight forward line?" Relevant info: All forces (represented by the arrows) in the diagram are equal in magnitude. The car trailer diagrams ...
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2answers
328 views

Quadrupole moment tensor definition

I'm not sure what the proper definition of the quadrupole moment tensor is. In the book on gravitational waves by Maggiore, the definition is $$M^{ij}=\int d^3x T^{00}x^ix^j. \tag{3.37}$$ ( Maggiore,...
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1answer
63 views

How to find the shear stress and bending moments of uninform distributed load [closed]

I can't for the life of me find a way to solve this. Given is the length of a T girder, which is fixed at one and on rolled support on the other side Now in the exercises given during class there ...
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2answers
139 views

Horizontal Beam Bending Due to Gravity

I just thought about this problem recently but am not sure where to find a solution. I am not certain which parameters are important in this problem, so please bear with me. Assume that a beam of ...
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4answers
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What is a moment?

As a 8th grader I am still a newbie at science and I have problems understanding the forces that I can not imagine and one of these "forces" is the moment. We are told that, $$\text{moment}= Nm$$ ...
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1answer
113 views

Is there a term for the first moment of mass?

If a stationary object has a rest-mass of say $2.0$kg and is located a distance $3.0$m from a particular point (of which it is stationary relative to). Is there some term to describe the moment of it'...
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2answers
69 views

How do I prove the total moment of horizontal and vertical components of a force is independent of point of application along the line of action?

How do I prove the total moments of the horizontal component, $\underline{x}$, and vertical component, $\underline{y}$, of a force, $R$, around a point, $A(\overline{x},\overline{y})$, is independent ...
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1answer
114 views

Torque/moment of force fundamentally

I've very much gotten used to calculating the torque about some axis of an object by multiplying the force and the distance from the axis at which the force acts on. We also know that if two opposite,...
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1answer
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Can a circular ring posses moment of area?

My civil lab exam constituted of 10 multiple choice questions. One of the question asked was if the "moment of area" of a solid circular plate was less than that of a circular ring of the same ...
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2answers
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Finding the moment about a Point [closed]

I am having a difficult time understanding when to use cos or sin when finding the moment of a force about a point. I understand that moment is $\rm force\cdot distance$. I have attached a picture of ...
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1answer
470 views

How does the rod's centre of mass change while falling?

Which force displaces the rod's centre of mass? The body is rigid and surface rough. And how can we apply conservation of energy in calculating angular velocity in presence of friction?
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1answer
441 views

Moment of a bent rod

In my mechanics textbook there is an example where they take the moment of the external forces in a system. The example states: Two uniform rods $OX$ and $XY$, pin jointed together at $X$, hang ...
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2answers
782 views

Are gravitational quadrupole moment, second moment of mass, and moment of inertia the same?

my understanding of moments is that they refer to distributions about an expected value, which allows us to make the multipole expansion. I read that: the zeroth moment of mass refers to the mass of ...
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2answers
3k views

Distribution of weight of an inclined object

We have a rod, 1m long and negligible height compared to the length, mass 10Kg uniformly distributed (center of gravity in the center). It is tilted theta degrees to the horizontal, and rests on two ...
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3answers
383 views

Why is the net torque 0 when pushing a block across a table?

The way I see it, when I push a block across a table, taking care to push in line with its centre of mass or just below, the object should topple over because the friction should create a (clockwise, ...
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1answer
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Why does the frictional centripetal force create a moment around a leaning bike?

Image source: https://geekswipe.net/science/physics/why-bike-lean-in-turn/ This diagram, along with several others I have seen, seem to use the centre of gravity as the pivot when calculating the ...
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1answer
135 views

What does it mean that direction of the resultant of cross product of two vector will be in a perpendicular direction to the plane of the vectors?

For example, moment of a force is represented as r × F. How is then the resultant in that direction ?
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1answer
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What is the highest order physically observable derivative of position?

Are there any physical models that compute higher-order derivatives of position than jerk, snap, crackle, pop, etc.? Can we measure higher-order, non-zero components?
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1answer
2k views

Calculate weight needed to balance a beam

I have found many sources to determine the weight or force needed for a balance moment, but not one that included the weight of the beam as a variable. I assume this is a very simple equation. Please ...
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1answer
590 views

Converting linear acceleration into moment

I am stuck on a simple physics problem. I have made a shaking test on an object, i have measured the acceleration at the top of the object and I would like to know what is the equivalent moment (or ...
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323 views

Can an electron have an electric quadrupole moment?

There are several groups actively working to measure the electric dipole moment of the electron. Is it possible for the electron to have higher order multipole moments, like quadrupole? The reason ...
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1answer
337 views

Help with formula for musical instrument [closed]

The formula is: $$ f = \frac{3.5161}{2\pi L^2}\sqrt{\frac{EI}{\rho A}} $$ $A$ = area, $\rho$ = density, $I$ = second moment of area cross section, $E$ = Young's modulus, and $L$ = length. Can anyone ...
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1answer
306 views

Resolution of horizontal forces about oblique axis

I am facing problem in resolution of moment. Here is the question along with my attempt at solution. I have always resolved forces and moments by using trigonometry. But here, when i use trigonometry ...
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1answer
243 views

second moment of area

I am having trouble understanding the term. How come that calculating the integral of the product of multiplying the Area differential by (distance)^2 determines the stiffness of the beam or so and ...
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1answer
447 views

direction of resultant moment about axis using scalar and right hand grip rule? [closed]

From the picture posted, this question is taken from my solution manual. I understand that using vector method of finding the resultant moment. I also know when we use scalar with right grip rule to ...
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3answers
301 views

About simple moment

Today I encountered a quite weird problem. There are two situations in the picture: The first situation: The cart move in a frictionless straight line from A to B The second situation: The cart ...
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1answer
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Toppling and friction

So the way I'll structure will be as follows: Scenario Question(s) The following would be conducted on earth with a gravitational field strength of 9.81N Picture a slope at 45 degrees from ...
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6answers
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What is the role of pillars in bridges?

As I can see in the picture, there are so many pillars which are holding the bridge. This picture gave a question to me that what are these pillars doing below the bridge?? An appripriate answer ...
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1answer
642 views

Moments of a barbell

For a barbell with 1. heavier weights near the centre heavier weights near the end (invert the order of the weights in the picture below) Will the barbell with heavier weights near the end be ...
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1answer
187 views

Moment of a force convention?

Two forces P and Q pass through a point A which is 4 m to the right of and 3 m above a moment center O. Force P is 890 N directed up to the right at 30° with the horizontal and force Q is 445 N ...
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3answers
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What's moment of weight?

I have googled this out but no where found my answer . My book states that the Centre Of Gravity of a body is the point about which the sum of moment of weights of all particles constituting the body ...
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2answers
543 views

Influence of couple-moment's position on bending moment diagram

The moment of two equally opposing force would create a couple-moment. Since the couple-moment value is invariant to the point considered to calculate the couple-moment, I can replace the two equally ...
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2answers
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Why is a clockwise moment negative by convention?

My physics book states that by convention a clockwise moment is said to be negative and an anti-clockwise moment is said to be positive. I'm curious about the origin of this convention. My thoughts: ...
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1answer
855 views

Why do objects topple on an incline?

Mathematically, I understand how to approach a question and to figure out if the object will topple over on an incline. I just want to understand why is it when the object's centre of mass is no ...
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3answers
106 views

What does the “moment” in the moment of force or the moment of inertia refer to? [duplicate]

According to the Merriam Webster dictionary: Moment - a very short period of time Does the word "moment" in quantities like the moment of force or moment of inertia refer to this colloquial ...
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1answer
3k views

What is the meaning of “moment”?

What is the meaning of moment? I'm little confused about the word as there are some terms like moment of momentum, moment of mass, moment of force, etc. I want to know what exactly is meant by the ...
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1answer
250 views

Center of mass/centroid changes between 2D and 3D?

Unless I completely botched the calculation, I noticed something strange: if you find the centroid of a 2d curve, and then revolve the curve around its axis then find the center of mass, the CM is ...
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2answers
723 views

Force distribution on corner supported plane [closed]

This question has been annoying me for a while. If you have a completely ridged rectangular plate of width and height x and y that is supported on each corner (A,B,C,D) and has force (F) directly in ...
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1answer
565 views

Scientific definitions of “moment (of)” and “instant”? [closed]

What are the scientific definitions of "moment (of time)" and "instant"? Are they different with their definitions in everyday language? I also don't know the definitions in everyday language, of ...
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4answers
2k views

Why does Torque exist?

Specifically, why does force increase with the moment arm? What about making a perpendicular force farther away from the axis of rotation increases it? How does the moment arm cause that?
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Forces on wheels in an accelerating vehicle

Assume that a motorcycle of mass $m$ has two wheels that are equidistant from its centre i.e the force on each wheel is $mg/2$. If the motorcycle accelerates forward, will the two forces on each ...
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1answer
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Clarification on what inertia and area moments?

This is something I have never understood despite applying the formulas in many classes. What I'm hoping to find here is some clarification. My understanding is that the first moment of inertia is ...